I’ve owned my 69 Dodge Dart four months now. It has good condition looking Road Hugger G/T radials on it. Hardly any tread wear. Here is the thing. The fronts were manufactured in 1999; rears 2000. I don’t know how many miles are on the tires. I’ve been reading up about “old” tires and how unsafe they may be although looking to be “good” tires. I live in WA state. The car was garaged and still is. Weather can be extreme cold to extreme heat. Mostly rainy though, mid temps. Should I replace all the tires? Thanks.

If it were me I would replace them based on age alone. I have never heard of "Road Hugger tires. Looks like they are some cheap house brand tires, those can be hit or miss. I would just get a set of brand name tires that aren’t made in China.

It’s the tires’ condition that matters, not their age. The fact that the car was kept in a garage helps.

There are many reasons why you could experience vibration at highway speeds. The simplest would be that the tires need to be balanced again. However, tires that are in balance don’t go out of balance by themselves. Maybe a weight came off or maybe one of them is beginning to come apart. If a tire is out of round, it can be in balance but still vibrate. Belt separation is a possible cause. So is a bent wheel. Considering the car’s age, everything in the suspension may be worn out.

Before you go much farther, take the car to a mechanic whose competence and integrity you trust and have him inspect the tires and the suspension. Then, you will know what does and doesn’t need to be done.

Even if there is no visible cracking of the rubber, and even if the belts are still good, the fact remains that the rubber compound of the tread does harden as it ages. A hardened tread compound will have MUCH less traction on a wet road.

After 10 years, the hardened rubber compound on these tires makes them much less safe on wet roadways, even if everything else about the tire looks good.